Conventionally, the virtual machine (VM: Virtual Machine) technology is known that runs multiple operating systems (OS) on a single server (a computer such as a workstation or a personal computer) to allow users to virtually use one computer, as multiple computers. Among products that use this technology are VMWare ESX Server from VMware Inc., Virtual Server from Microsoft Corporation, and Xen from XenSource Inc. (U.S.). Those products allow the user to issue a VM generation command to start a new virtual machine on a server.
Another system using the virtual machine technology is a thin client system. A thin client system is a system in which the operation computers of multiple employees are consolidated into a virtual machine on a server, and the employees operate this virtual machine from terminals via a network. Using a high-performance computer for the routine jobs of company employees is inefficient and, so, the employee's computers are consolidated into a server as a virtual machine to increase the usage efficiency of computer resources. In addition, consolidating the job data used by the employees onto a server enhances security, for example, prevents information from being leaked.
For use in a computer system in which multiple servers are connected via a network, a still another technology is known in which a virtual machine, started on one server, is moved to another server. For example, VMware provides vMotion, and Xen provides ‘migration’ that is the virtual machine movement function.
When a new virtual machine is started in an environment in which multiple servers are dispersed, a method for selecting a server that has sufficient resources is employed as described in Patent Document 1. The technology disclosed in Patent Document 1 is that, based on the measurement data indicating the performance of existing virtual machines on a predetermined time basis, a combination of virtual machines and servers that maximize the total of the performance values of the virtual machines at each time is calculated, asynchronously with the start of a new virtual machine, when each virtual machine is run on one of multiple servers. And, the virtual machines are rearranged based on the calculated combination.
Patent Document 1:
    Japanese Patent Kokai Publication No. JP-P2005-115653A